From: Garey Barrell 
Subject: Re: e: [drakelist] T4XC and D104


Garey Barrell  made an utterence to the drakelist gang
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Peter -

The amplifiers were added to crystal microphones for two main reasons. 

1.  Eliminate the extreme sensitivity of the crystal elements to the 
input impedance of mic input circuits.  Older tube transmitters were 
usually at least 100k ohms up to almost 1M.  The lower the impedance 
seen by the crystal cartridge, the more pinched and tinny the audio 
becomes.  The bass response goes first and then the mid-range peak 
starts to go up as the load z goes down.  This was the original reason 
for the amplifier in the UG-8 stand for the D-104.

2.  Solid state rigs have generally lower mic input impedance, often as 
low as 500-600 ohms.  The amplifier has a very low output impedance 
while reflecting a constant high impedance to the crystal cartridge.  So 
it's capable of driving low z mic inputs, yet can put out the higher 
voltage required by the older hi z rigs.

The CB crowd discovered that cranking the mic amplifier gain way up 
added a certain "distinctive" sound to their transmissions, similar to 
the effect offered by some of the classic tube guitar amplifiers!!

The amplified mics generally give a smoother, more consistent audio over 
the frequency range than the cartridge alone driving various input z.  
The trick is to have the transmitter gain high enough to get into the 
good signal/hum part of the transmitter mic stages and operate the VOX 
reliably, and then turn up the mic amp gain for full modulation.

73, Garey - K4OAH
Atlanta


PWells wrote:

>
> PWells  made an utterence to the drakelist gang
> ----------------------------------------------------------------------
> Dear group
> I've got an ols Turner '+2' amplified mike. I wonder if its the same 
> thing for the CB crowd because I have an older similar Turner that's 
> without the amp.
> Anmy opinions
> 6
> 73's
> VE2FAR
> Peter
>
> ----------------------------------------------------------------------
> On Behalf of PWells 
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On Behalf of Garey Barrell 
Submissions:        drakelist{at}www.zerobeat.net
Unsubscribe:        majordomo{at}www.zerobeat.net - unsubscribe drakelist in body
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Zerobeat Web Page:  http://www.zerobeat.net
Brought to you courtesy of TLCHost.net  http://www.tlchost.net/
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